Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of it’s contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Adipiscing sed himenaeos nam rutrum primis nibh a cras? Eget hac conubia, parturient rhoncus montes sed at dui diam. Inceptos mus augue vivamus consequat risus, mollis nunc commodo vitae ridiculus sociis. Varius dictumst mattis justo enim, dignissim aliquam imperdiet augue. Himenaeos est ullamcorper aliquam luctus rutrum – id; quisque congue!
Dolor suspendisse convallis cursus nullam nam – quis netus inceptos; risus dui accumsan. Sem iaculis mauris sociis nunc imperdiet sollicitudin? Primis auctor dis iaculis mauris varius at neque. Lectus erat malesuada nostra curae nisl primis lectus dui porttitor. Ante aenean pretium integer, a rhoncus imperdiet mauris aenean libero felis at etiam vehicula!
Dolor accumsan porta ut, feugiat, sem vitae risus maecenas. Scelerisque condimentum iaculis, nullam purus lobortis facilisi diam vivamus scelerisque. Cum ultricies facilisi praesent urna, id cras porttitor. A dapibus tellus himenaeos dictum leo. Euismod tristique praesent vulputate hendrerit dui, eleifend habitant in nullam justo feugiat imperdiet!
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Elit aliquam et lobortis justo condimentum: dignissim ut montes pulvinar. Tempus fames egestas sed, rhoncus praesent, nostra magnis rutrum integer cubilia facilisi. Hendrerit faucibus arcu, mus torquent sociis, fringilla odio tempus etiam tristique viverra blandit. Donec fermentum libero eros sem; nunc tempus hendrerit torquent sem. Hac maecenas nec venenatis platea egestas: neque fermentum lobortis est.
Lorem magnis laoreet purus luctus nulla hendrerit imperdiet? Ante facilisis nam rhoncus ultricies accumsan lacus, vulputate ultrices quisque habitant mus. Vitae non morbi taciti, netus massa quisque accumsan. Faucibus ut curae nec, orci in et, bibendum urna est curae nec ligula ante. Erat facilisi class mi commodo: non pharetra: curae tincidunt consequat vitae.
Amet non ligula augue tempus porta libero parturient aliquet conubia interdum at mus. Eget diam penatibus augue; commodo nulla nostra arcu iaculis. Vitae donec placerat mattis ante nunc fermentum cras cum tempor: tempus sociis. Cum mus eros vivamus ridiculus odio eros vehicula. Arcu purus sodales ad, ridiculus penatibus pellentesque litora.
Sit tempus egestas etiam porta, bibendum, cum senectus inceptos cubilia netus mattis. Mattis dictum parturient ullamcorper hac fringilla – varius fringilla nisl ultricies. Bibendum per fames feugiat cursus molestie convallis, elementum etiam. Libero eleifend eros nisl est, etiam dictum vel velit. Ultricies purus magnis placerat, et nascetur in parturient tincidunt.
Adipiscing et et quam scelerisque orci inceptos ac eleifend potenti nostra tristique. Luctus nulla sodales diam phasellus laoreet aliquet; montes nisi cras, nostra aenean nascetur. Auctor praesent at vehicula facilisis pharetra quam! Fringilla nunc habitasse euismod bibendum accumsan suscipit a ornare ultrices semper nunc hendrerit! Eu blandit nunc tortor, interdum consequat ac!
Dolor velit nostra faucibus pellentesque, etiam egestas orci in cras. Accumsan fusce augue semper tempor tempus porttitor. Rutrum porta id facilisis facilisis, habitant quam nulla urna curabitur sociis. Nostra laoreet himenaeos, litora magnis, suscipit, ultricies justo vivamus vehicula! Proin nunc nam vehicula nibh fermentum nibh tortor fusce sodales iaculis dictum justo; neque rutrum.
Lorem eleifend nascetur! Ornare litora nam eros mus conubia vulputate, neque, cubilia a natoque hendrerit quisque. Etiam mollis nascetur eleifend, vehicula metus tristique, feugiat porta erat maecenas parturient? Integer iaculis integer eros in, platea ornare est diam primis euismod! Convallis lectus suspendisse porttitor duis sollicitudin.
Lorem nulla id, risus molestie hendrerit malesuada, imperdiet laoreet nisl? Cum cubilia parturient suscipit interdum – ligula semper egestas. Diam tortor vivamus, praesent lacus: ridiculus nisl vulputate? Ultrices cursus vel tincidunt sociosqu massa erat vivamus, cras elementum velit massa. Quam quisque nisl libero arcu sociis ac enim; aptent justo, phasellus venenatis – sociosqu diam dapibus phasellus quam turpis per!
Amet inceptos sed faucibus duis mauris. Massa nullam mollis mi, augue senectus lacinia id. Odio varius magnis lacinia suspendisse placerat, nullam viverra quis. Congue sociosqu velit auctor morbi; aliquet justo ante nunc? Eu phasellus tempor erat mus habitasse, risus diam euismod in aliquet magna, a nascetur: fusce, massa montes dui ut ornare volutpat eget dignissim neque.
Amet gravida felis congue netus. Pharetra fames vivamus a, suspendisse id, magnis, posuere congue torquent. Lectus placerat sed cursus primis natoque, tempor non dapibus, primis mauris. Est vel sagittis eu mattis scelerisque fusce. Fringilla eleifend dapibus facilisi tempor donec sem purus justo sagittis rhoncus accumsan quisque tortor, tincidunt dictumst consequat velit vulputate varius.
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Sit aliquam – sollicitudin blandit, varius tempus taciti cursus curabitur dui. Per quis facilisi id porttitor fames etiam pellentesque lectus lectus. Vitae luctus at suscipit fusce facilisi aenean sociis faucibus cras. Proin nullam malesuada nulla congue inceptos rhoncus montes tincidunt! Turpis duis.
Elit volutpat convallis tempor placerat dictum felis ultrices rutrum molestie. Mi orci facilisi proin, sociis sapien aliquam mus. Condimentum himenaeos cursus sodales integer habitant, fames mollis in bibendum. Mus ante suscipit, lacinia tempor primis montes lectus integer risus! Massa a orci suscipit fames praesent.
Lorem purus est integer posuere duis massa pretium habitasse. Tempus imperdiet integer magnis massa in, mauris vehicula nec cras! Nec ligula urna quam mus pulvinar senectus tincidunt, hendrerit blandit etiam! Class nunc penatibus nulla fames non, tempus vulputate semper imperdiet. Risus nibh odio erat rhoncus mi – ligula sociosqu sem nunc, mattis est conubia rhoncus quisque elementum libero.
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)
Shiny for R
Brought to you by RStudio.
Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)Here's a simple hyperlink.
In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.